Although methicillin-resistant Staphylococcus aureus (MRSA) infections have historically been associated with higher hospitalization costs, in recent years costs associated with methicillin-susceptible S aureus (MSSA)-related infections have been trending higher than costs associated with similar MRSA-related hospitalizations, according to a study recently published in Clinical Infectious Diseases.

Traditionally, MRSA infections have been associated with worse patient outcomes and higher costs of care than MSSA infections. However, since those studies are a decade old, this trend may have been altered in recent years by changes in the insurance landscape and development of new diagnostics. Additionally, newer statistical methods allow for improved analysis of outcomes and cost differences between patients.

Understanding the magnitude of, and trends in, the excess costs of resistant infections is necessary for the development of rational responses to the growing public health crisis of antibiotic resistance. Although studies have examined cost differences between MRSA and MSSA infections at the hospital level, there is a lack of information on cost differences at the national level in the United States.

Therefore, this retrospective analysis provided updated estimates of the excess costs associated with resistant S aureus infections using data from the National Inpatient Sample from the Agency for Healthcare Research and Quality from 2010 to 2014. Costs for hospitalizations associated with MRSA- and MSSA-related septicemia and pneumonia infections, as well as MRSA- and MSSA-related infections from conditions classified elsewhere and of an unspecified site were calculated. Differences in the costs of hospitalization were estimated using propensity score adjusted mortality outcomes.

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There were no large differences in demographics, length of hospital stay, Charlson score, or risk mortality scores between patients with MRSA- and MSSA-related hospitalizations in any year. Results showed that pneumonia and sepsis-related hospitalizations had the highest estimated costs in 2014. Propensity score-adjusted costs were significantly higher for pneumonia related to MSSA ($40,725) vs MRSA ($38,561; P= .045). Costs for other unspecified hospitalizations associated with MSSA ($15,578) were also significantly higher compared with MRSA ($14,792; P <.001). These similar patterns were seen throughout 2010 to 2013, but cost differences between MSSA- and MRSA-related pneumonia hospitalizations rose from 25.8% in 2010 to 31.0% in 2014. The research also demonstrated MRSA-related hospitalizations to be associated with a higher mortality rate when compared with MSSA-related hospitalizations.

Overall, the study authors conclude that, “Contrary to historical studies at the hospital-level, we found that nationally, MRSA-related hospitalization costs were approximately the same as or less costly than MSSA-related infections.”